7 March 2024 11:44 pm
Officers were responding to an emergency call placed at approximately 22:52 local time (03:52 GMT) on Wednesday when they found the six people.
Ottawa police chief Eric Stubbs has described the incident as a "mass shooting".
Police said one male suspect has been arrested.
Sri Lanka's High Commission in Ottawa told the BBC on Thursday that the victims were a family of Sri Lankan nationals.
The commission did not provide further details, referring questions to police.
In a statement early on Thursday morning, the Ottawa Police Service called the investigation into the deaths "tragic and complex".
Officials have also said that at least one person had been taken to hospital in the Ottawa area with serious but not life-threatening injuries.
They added that there was no ongoing threat to public safety.
Chief Stubbs called the incident a "real tragedy" that would continue to have a "significant" impact on the whole city.
"Obviously, it's a horrific scene," he said during an early morning interview with CTV News.
He added that police did not believe it to be a domestic or intimate partner related incident.
"I'm sure the impact on the community is great," he added, while emphasising that residents and community members should continue to stay away from the area.
In a separate interview with CBC News on Thursday, he referred to the incident as a "mass shooting".
Local news reports that there were police cars parked outside the house in the Barrhaven neighbourhood.
In Toronto on Thursday, Prime Minister Justin Trudeau expressed "shock and horror" at the incident, which he called a "terrible violence".
Ottawa's mayor called the multiple homicide event "one of the most shocking incidents of violence in our city's history".
"We are proud to live in a safe community but this news is distressing to all Ottawa residents," Mark Sutcliffe wrote in a post on X, previously known as Twitter.
"Thank you to our emergency responders who are investigating and supporting those who are affected by this terrible event," he added.
A news conference about the investigation, which has been passed to the Ottawa Police Homicide Unit, will be held on Thursday afternoon.